In the past, straw was not considered a suitable structural material. Unlike wood, straw has not been considered for its strength and has not commonly been considered as a building material. Current trends in the use of straw for construction involve straw bales where dense packing and size provide necessary strength and structural support. Straw represents a vast source of fibre that, when properly processed, has economic potential as a substitute for wood in structural applications.
In the description that follows the term cereal straw is to encompass other lignocellulosic material that is cereal straw-like in structure, such as rice straw and bamboo. Heretofore a thin panel of compressed non-woody lignocellulosic material (i.e. straw) has been made by mixing short straw pieces with a binder. Disclosure of this thin panel is found in U.S. Pat. No. 5,498,469 in the name of Howard et al. issued Mar. 12, 1996, incorporated herein by reference. The panel is used as a core layer or core stock in a plywood laminate; thus a thin layer of straw panel, is sandwiched between two layers or sheets of plywood. Although this thin panel .about.0.10 inches appears to perform its intended function, the thin panels do not have sufficient strength as structural boards. The panels were incorporated with stronger wood laminate layers for the production of plywood.
Other references relating to fiber panel methods of manufacture and devices for making such panels are: U.S. Pat. No. 5,730,830 in the name of Hall, issued Mar. 24, 1998; U.S. Pat. No. 5,729,936 in the name of Maxwell, issued Mar. 24, 1998; and, U.S. Pat. No. 5,728,269 in the name of Kohno et al., issued Mar. 17, 1998.
Inventor discloses in patent application Ser. No. 09/119,041 that the straw strands have to be split into longitudinal pieces, to ensure that the exterior and interior surfaces of the hollow straw stem core are coated with a binder prior to hot pressing in order to obtain maximum strength. To increase bending strength and stiffness the strands have to be oriented such that the straw strands are substantially parallel. Furthermore, bending strength and stiffness increases substantially with the length of the split straw strands.
Available prior art devices such as a grain roller mill, a ringflaker or a hay macerator may be used for splitting the straw. Unfortunately, these devices do not produce split straw strands necessary for making a structural panel, board or beam out of straw that meets requirements concerning strength and stiffness. The split straw strands are mostly short or the straw has not been split adequately such that the strands are not separated making it difficult or even impossible to orient the strands. In U.S. Pat. No. 5,236,319 in the name of von Allworden et al. issued Jul. 5, 1994, a device for preparation of straw materials is disclosed. With this device mowed straw material is broken up into fibers by feeding it into a clearance zone between planetary rolls and a central roll, in order to speed up the drying process. Unfortunately, this device does not split the straw into separated strands necessary for aligning the split straw strands. In U.S. Pat. No. 5,119,562 in the name of Dietz issued Jun. 9, 1992, a hand tool for splitting straw into strips is disclosed. Although, the device produces long separated split straw strands it is not feasible for use in manufacturing structural panels out of straw. The device allows processing of only one piece of straw at a time and is only useful for producing a straw mesh or wickerwork by hand.
It is an object of this invention, to provide a device for splitting longitudinally pieces of cereal straw into long separated strands for use in making a panel, board or beam.
It is another object of this invention to provide a device for aligning the split straw strands.